The amount of money transacted through leading online loan services has skyrocketed to $5.1 billion in four years. And so, it is no surprise that VCs and private equity firms are throwing more money into services like Prosper and lesser-known startups like CommonBond.

But with the field of online lending services now well-seeded with startups, pressure is mounting on these richly funded companies to give investors a return. So far, it isn’t clear whether the public markets are a good fit—Lending Club’s stock has sunk 34 percent since its peak last fall. And there have yet to be any major acquisitions of online lending companies.